At a mountaintop observatory near Coonabarabran in north-western New South Wales, a team of astronomers are searching for wiggles.

Not the all-singing, all-dancing variety, but the faint imprint of sound waves left in the light patterns of thousands of galaxies formed after the Big Bang nearly 14 billion years ago.

Scientists hope these wiggles will be able to shed some light on what we cannot see — dark energy, a mysterious force thought to have been speeding up the expansion of the universe for the past nine billion years.

Understanding the nature of dark energy from research like this will not only allow us to better understand the distant past, but also the very future of our universe.

The universe accelerates

In the 1920s, Edwin Hubble noticed the light from distant galaxies moving away from Earth faster than light from galaxies nearby. His observation that the universe was expanding later led to the Big Bang theory.

For the next 70 years after Hubble's discovery, astronomers theorised that the expansion of the universe would slow down over time due to the combined gravitational attraction of the hundreds of billions of galaxies.

Then in 1998 two research groups from Australia and the US realised the opposite had occurred.

While searching for supernovae to measure the rate at which the expansion of the universe was slowing down they found something mysterious had taken over from gravity as the dominant force in the universe between eight and nine billion years ago, and was pushing apart stars and galaxies at near light speeds.

Supernovae are perfect for measuring the expansion of the universe because they emit a known luminosity, or amount of light. By measuring the relative brightness of a supernova you can determine how far away from you it is.

By looking at the colour of the supernova you can also determine its redshift: how much of its light has shifted towards the red end of the spectrum, as the universe expands and its light is stretched as the supernova moves away from you. The relationship between distance and redshift for many supernovae can then tell astronomers whether the expansion of the universe is accelerating or slowing down.

The researchers found the supernovae were dimmer than theorists predicted — so the universe must be speeding up, not slowing down.

"[The discovery was] the equivalent of throwing a ball in the air and having it go into orbit," says astrophysicist Professor Brian Schmidt from the Australian National University, leader of the Australian team. "It's kind of a surprise."

While astronomers still don't know much about the force that is causing this acceleration, they did give it a name: dark energy.

What is dark energy?

Dark energy does not emit light so it cannot be observed directly. Instead scientists infer it is there by the effects it has on the expansion of the universe.

Colless, who is also involved in the WiggleZ project, says many theories have arisen over what dark energy is. Albert Einstein started the ball rolling early last century when he was working on his general theory of relativity.

Einstein introduced a 'cosmological constant' into his equations, which allowed for the possibility of a repulsive anti-gravity force to counteract the gravitational pull of matter. It also made his equations fit with the prevailing view of the time that the volume of the universe was static.

When Hubble discovered the universe was expanding, Einstein removed the constant, describing it as his "biggest blunder".

But in 1998, the Australian and American teams realised that Einstein may have been right all along: a 'cosmological constant', or something similar, was responsible for the universe's acceleration.

Schmidt says dark energy is part of space itself.

"You can't disentangle it from space," he explains. "The more space is created, the more dark energy is created. It also pushes away from itself, which works in the opposite direction to gravity."

Researching the wiggles

Australian scientists hope to test the current theories of dark energy by studying thousands of distant galaxies formed at different times after the Big Bang, particularly galaxies formed about eight to nine billion years ago when dark energy began to dominate gravity.

Andromeda (pictured) and our own Milky Way galaxy will collapse and form super-galaxies if the expansion of the universe keeps accelerating
(Source: X-ray: NASA/UMass/Z Li, QD Wang; Infrared: NASA/JPL-Caltech)

Using the Anglo-Australian Observatory near Coonabarabran in NSW, the WiggleZ project is measuring wiggles or imprints of sounds waves left in the light patterns of these galaxies.

Billions of years ago, sound waves spread throughout the early universe. As the universe expanded, the distance between the peaks of each wave also increased. Because clusters of galaxies formed on the peaks of these sound waves, the WiggleZ researchers can measure how the spacing between the peaks has changed over time by measuring the distribution of these galaxies.

Scientists first identified wiggles in the cosmic microwave background radiation, or background heat, produced when the universe was only 300,000 years old.

"Our technique involves measuring the [imprints of these sound waves, left behind as wiggles in the light patterns of] about 300,000 galaxies over a very large volume of the universe," says Professor Warrick Couch, a lead investigator on the project.

If they know the distance between the peaks of the sound waves, they can measure how fast the universe has expanded over different eras, and potentially show that something — dark energy — is accelerating this expansion.

Due to be completed by mid-2010, the WiggleZ project is the first survey of its kind that allows astronomers to test different theories of dark energy by looking at much more remote parts of the universe.

The WiggleZ project is only one of a number of dark energy experiments in the works. NASA and the US Department of Energy are planning to launch a US$1 billion-plus Joint Dark Energy Mission in the middle of the next decade, which will hopefully advance our knowledge of matter, space and time.

Does dark energy even exist?

Some question whether the supernovae studied in the 1998 surveys are fainter than first thought, are perhaps closer than they appear or that their dimness is due to other effects.

University of Canterbury physicist Dr David Wiltshire believes most researchers accept dark energy as a theory because scientists since Einstein have used models that are too simple, assume that the universe is homogenous and that laws of physics work the same everywhere.

He argues that the standard model struggles to explain the 'lumpiness' of the universe observed today — clusters of galaxies strung in filaments and great walls around voids 150 million light years across.

There are alternative theories to explain the so-called effects of dark energy such as quantum theories of gravity, or suggestions that the Earth is in the middle of an emptier than normal region of space, and the expansion of the universe is not uniform.

"The field of cosmology developed for decades when there were no good observations, and we are reaping that history now; observations are far in advance of theory," Wiltshire says.

However, WiggleZ project leader Dr Michael Drinkwater does not believe the models are over-simplified: "The basic framework we use leads us to conclude the universe is dominated by dark energy and cold dark matter," he says.

Drinkwater says the standard model of cosmology explains many different observations of the universe, both on large and small scales.

"It would require some extremely unusual results to question the basic model," he says.

A dark future

While research continues into dark energy, Anglo-Australian Observatory's Colless is confident the mystery will be solved within the next five to 10 years.

"How old is the universe? What will happen to it? We can't answer these questions unless we know what dark energy is," he says.

ANU's Schmidt agrees. He says the night sky will look nothing like it does today if stars and galaxies and everything in between continue to be pushed apart by dark energy at ever increasing speeds.

"If the universe keeps on doing what it is doing, pretty much all the galaxies we see today will be it," he says. "Very few [new] ones will form. The Milky Way and Andromeda galaxies will collapse and form super-galaxies.

"There will still be stars in the sky from our own galaxy but there will be no other galaxy in the sky."

And so the hunt for this mysterious force continues.

Dark matter? Is it the same thing as dark energy?The atomic matter that makes up stars, planets, trees and animals only accounts for four per cent of the universe. The rest is made up of phenomena that we can't see: dark energy and something else called dark matter.

Scientists know dark matter exists and that it makes up 21 per cent of the universe, but they don't know what it's made of.

The first evidence of dark matter emerged in the 1930s when astronomers discovered that the mass of all the visible material in a cluster of galaxies was far less than the total mass of the cluster.

They described it as exotic particles such as 'weakly interacting massive particles', or WIMPs, because it interacts very weakly with ordinary matter.

Though dark matter cannot be observed directly, its presence is given away by the effect of its own gravity on objects in space, such as in the motion of distant stars and galaxies. It is thought to act like a 'gravitational glue' keeping these stars and galaxies from falling apart.

As it stands, there is at least seven times more gravity in the universe that can be accounted for with atomic matter.

Unlike ordinary matter, dark matter does not reflect or emit light. Nor can it be recreated on Earth.

It is thought to be cold because it is undetectable to infrared and X-ray telescopes. It's possible that it could zip through our bodies every few seconds just as elementary particles like neutrinos from the sun pass through the Earth.

ANU's Schmidt says there is no evidence dark matter and dark energy are linked: "We have two things which do not emit light and are very difficult to pin down because they are not like the stuff we are made up of — atoms."

Jim Thornton :

Robbie :

03 Apr 2009 6:09:24pm

Magnetism is just the result of applying general relativity to electrostatics. These developments were able to describe all forces which act on the cosmic scale into one equation. The problem is that there is an unexplained constant. Scientists think that it might be a result of dark energy.

please explain :

04 Apr 2009 10:08:32am

I'm a little confused.By looking at the stars and galaxies we are looking at the past so if Hubble found that the light from distant galaxies (ie further in the past) is moving away faster than closer galaxies (closer to our present) then doesn't that suggest that the universe is slowing down? This article didn't explain how the intrinsic brightness of an object suggests that the universe expansion is speeding up. Am I missing something? This is a very interesting area of science and I'd love to understand it better.

Brian Schmidt :

07 Apr 2009 11:43:57am

So Hubble found that the further galaxies are away, the faster they appear to be receding away from us. This is seem as a consequence of an expanding Universe. That is, if you stretch the universe at a constant rate, from any vantage point, the further an object is in distance, the faster it recedes...

I have a little diagram on this at http://www.mso.anu.edu.au/~brian/PUBLIC/images/expand.gifwhich you can read more fully at http://www.mso.anu.edu.au/~brian/PUBLIC/public.html

What we have seen is that the rate objects move away from each other back in time is slower than it is now - that is the Universe has sped up. We do this essentially by comparing the distances to objects with their rate of recession as a function of time. The URL above provides a more comprehensive description of the process.

Kostas :

12 May 2009 11:25:50pm

Pardon my ignorance Brian. I cannot get past the fact that the further an object is the faster it moves away (as a consequence of expansion of the fabric of space), however, if we are looking far away, we are looking far into the past, so if the galaxies from the past are moving away faster, then this means that earlier in the history of the Universe, the expansion was faster and it is therefore slowing down. I had a look at your site - I can't see past this, what am I missing?

Gary :

Kris Kuitkowski :

05 Apr 2009 10:25:58am

I am very much surprised how long scientists will keep inventing "patches" to repair faults in existing theories. Dark matter, dark energy, black holes, they are all consequences of one faulty theory of gravity, which for some unknown reason scientific world desperately is trying to repair. Wouldn't it be easier and more sensible to assume there is no magical attraction force between particles; that the forces which push galactic apart are caused by more energy being imparted from "inside" than from "outside"? When you see a sailboat on the lake moving to one of its banks you can say that it is "attracted" (like being pulled by invisible rope)to it, but it would make much more sense to state that the wind is pushing the boat.Any supposed attraction implies some sort of connections between the bodies.It is reasonably easy to prove that if energy coming from universe would be slightly absorbed by the matter and if 2 objects are in each other shadow, the net push (or "attracting") force would be proportional to the product of their mass.

Brian Schmidt :

07 Apr 2009 11:58:26am

This is a valid criticism, as we have had to patch the simplest model of the Universe - one that obeys Einstein's equations and is only made of atomic matter by inventing two forms of matter - Dark Matter and Dark Energy.

The reason why we continue with this patch, is that it is still the simplest model of our Universe that predicts what we see. In 1998, when we discovered the accelerating Universe, it was possible to predict what the Cosmic Microwave Background observations would look like. These predictions agree almost perfectly with what is seen. The model you refer to does not naturally explain the Cosmic Microwave Background, does not explain nucleosynthesis, does not explain pulsar observations, etc...That is why it is not in favour by people like myself.

Let me state that I am open to new models - but they need to be predictive and testable - that is what my role in science is - to test out theories.

rDawg :

watch_this :

07 Apr 2009 2:22:16pm

You are thinking about scientific discoveries all wrong.As physicists, cosmologists and astronomers delve deeper into they big question of HOW, they uncover more things, and know while their theories are correct, they are incomplete.Think of it like your see a road sign in the distance. You don't know what the road sign is, and so describe it as a square. As you get closer, you realise that you were missing some details. Yes a sign is a square, but it is a square with a pole coming out of the ground.You get closer again and realise that your previousd description, again, while correct was still incomplete. You realise that a sign also is green with white squiggles on it. This continues until you get close enough to be able to accuratly describe what the sign is. This is physics, and the sign is the universe. The more we scratch, the more we find, and the more we need to explain. As it stands we are currently seeing a square on a pole driven into the ground.It is an exciting time to be around, and within our lifetime we can expect many more discoveries to come. A black hole is simply an object whose escape velocity is greater than the speed of light, many of such objects having been detected over the past 20 years.

James :

06 Apr 2009 1:37:17pm

Could it be that Dark Matter could be matter that is so close to 0 K that it has fallen apart? I seem to remember reading an article in Scientific American (around 1990) that stated that as matter approached absolute zero the cohesive forces holding atoms together 'break down'.

jj :

watch_this :

07 Apr 2009 2:27:22pm

You have just described one of the leading candidates of particles thought to cause dark matter - WIMPs - Weakly Interacting Massive Particle - basically a heavy particle that doesn't interact very well with the electro-magnetic force - physicists are already all over this one.

daliere :

Brian Schmidt :

07 Apr 2009 12:09:07pm

anti-matter actually behaves just like normal matter, gravitationally. I always like to say the reason we call matter, matter, and anti-matter anti-matter, is because there is a lot more matter than anti-matter. Otherwise, they more or less work the same - they just don't like being in the same place at the same time.

watch_this :

07 Apr 2009 2:29:43pm

It is currently thought that anti-matter reacts the same way to gravity as ordinary matter. The main difference between normal matter and anti-matter is anti-matter has the opposite electrical charge to ordinary matter.Hopefully we'll know a definitive answer to this through experiments being conducted on anti-matter streams over the next couple of years.

Greg :

07 Apr 2009 11:48:59am

Imaginative response :)Could the big bang have been matter entering a new realm from another at a particular point, ie. matter escaping from one big balloon and creating another balloon beside it. Thus, dark matter could be entering our balloon and simply pushing all before it.

Kostas :

12 May 2009 11:42:17pm

Samander, We know what we know about Science, it is likely that what we know is very little, but it is the most we have ever known. It's a very exciting time now, with so many possible theories and some instruments like LHC that are at the verge of proving and disproving many theories, and as a consequence the creation of better theories again.

wisdom4u2luv :

Andrew :

08 Apr 2009 2:09:16pm

what if dark energy is the part of a attom that spins around it and has slowed down and lost its charge from the attom this being a kind of energey and at the same time a type of gravity that is sucking the charge of gravity in turn pushing everything apart or just letting them let go trying to recharge its self like a flat battery

John Prytz :

09 Apr 2009 8:26:09pm

I've obviously lost something in translation somewhere, but I was under the impression that 'dark energy' was just the vacuum energy, otherwise known as quantum fluctuations or the quantum jitters. I believe that the vacuum energy has been experimentally verified, albeit apparently some 120 orders of magnitude less than theory would predict.

jcwalker3usa :

10 Apr 2009 4:39:47am

Dark Matter or for that Matter Darkness

The fact that Italy has substantiated its initial report on the discovery of Dark Matter might raise one's eyebrow in contemplation of the many discoveries or mysteries that will be forthcoming but what about the question of darkness itself. Now we know that darkness is the absence of light or the sensation of it but what about all the other mysteries in the Magnetic Spectrum including visible light and one might say that dark matter, as we know it, is only part of this marvelous wonder. There is not one part of our sensory world that does not involve the Magnetic Spectrum and looking further into this wonder of God one realizes that everything we experience, whether solid, gas, liquid, time or space has some part in the Magnetic Spectrum attached to it, around it and even created by it. Once one discovers that Darkness has a wave length then one can discover this wave length varies according to its density. So Darkness (aether) is an integral part of the Magnetic Spectrum making up the very matrix of space.The so called void of space is indeed quite the contrary when one considers darkness as part of the magnetic thin fabric that is our Universe.

Dennis :

01 May 2009 11:55:29pm

I put forward this idea in another forum without a single comment, it seamed to me to explain Hubble's law and the expansion of the universe."The aftermath of the Big Bang or the expansion of the universe was Gravity expanded travelling at the speed of light but matter couldn't keep up, it continued to try and fill the void. Therefore you have two volumes of space 1 at a perfect vacuum and absolute zero temp i.e. 273 deg Kelvin. That's where gravity is expanding the universe boundary. The other volume of our universe that contains matter is at a slightly higher pressure and temperature.Force = pressure x area. Acceleration =force / massSo the universe expands since the gravitational sphere expands faster than the matter can follow the expansion rate of the universe increases."I like simple answers, but the above maths is for experts.

Mick :

Dennis :

26 May 2009 2:43:16pm

Thankyou for your reply and of course you are correct about absolute zero. An error made out of a combination of nervousness, too many years out in the blue collar workforce and too many braincells now deceased. Not sure why I earned your ire but at least I can say now that I had a reply. 100% of respondants pointed out I was wrong.Perhaps I shall in future just read the articles go oh ahh and leave it at that. Once again thanks for your reply.

Richard :

19 Jun 2009 3:06:12pm

I would be interested to hear a comment on the relationship between dark and light matter. Does dark matter give rise to light matter? If galaxies are the "beacon on the hill of dark matter" is the beacon fuelled by the hill itself? I suspect that this is unanswerable and not just because we don't know what dark matter is.

mmfiore :

22 Jun 2009 9:39:00pm

We are a group that is challenging the current paradigm in physics which is Quantum Mechanics and String Theory. There is a new Theory of Everything Breakthrough. It exposes the flaws in both Quantum Theory and String Theory. Please Help us set the physics community back on the right course and prove that Einstein was right! Visit our site The Theory of Super Relativity: http://www.superrelativity.org/html

**The onset of big-bang's inflation started gravity, followed by formation of galactic clusters that behave "classically" as Newtonian bodies while continuously reconverting their shares of pre-inflation masses back to energy, and of endless intertwined evolutions WITHIN the clusters in attempts to resist this reconversion.

Astronomically there are two "physics", a "classical physics" behaviour of and between galactic clusters, and a "quantum physics" behaviour within galactic clusters.**

A. "Heavyweight galaxies in the young universe", at

http://www.sciencenews.org/view/generic/id/42419/title/Heavyweight_galaxies_in_the_young_universeNew observations of full-grown galaxies in the young universe may force astrophysicists to revise their leading theory of galaxy formation, at least as it applies to regions where galaxies congregate into clusters.

B. Some brief notes in "Light On Dark Matter?"

- "Galaxy Clusters Evolved By Dispersion, Not By Conglomeration"- Introduction of E=Total[m(1 + D)] - "Dark Energy And Matter And The Emperor's New Clothes"- "Evolutionary Cosmology: Ordained Or Random"- "â€śMovieâ€ť Of Microwave Pulse Transitioning From Quantum To Classical Physics"- "Broken Symmetry" Is Physics' Term Of Biology's "Evolution"- "A Glimpse Of Forces-Matter-Life Unified Theory"

C. Commonsensible conception of gravity

1. According to the standard model, which describes all the forces in nature except gravity, all elementary particles were born massless. Interactions with the proposed Higgs field would slow down some of the particles and endow them with mass. Finding the Higgs â€” or proving it does not exist â€” has therefore become one of the most important quests in particle physics.

However, for a commonsensible primitive mind with a commonsensible universe represented by E=Total[m(1 + D)], this conceptual equation describes gravity. It does not explain gravity. It describes it. It applies to the whole universe and to every and all specific cases, regardless of size.

2. Thus gravity is simply another face of the total cosmic energy. Thus gravity is THE cosmic parent of phenomena such as black holes and life. It is the display of THE all-pervasive-embracive strained space texture,

Dov Henis :

- Dark energy and matter YOK. Per E=Total[m(1 + D)] all the energy and matter of the universe are accounted for.

- Higgs Particle YOK. Mass begins to form at some value of the above D.

- Sleep is inherent for life via the RNAs, the primal Earth organisms formed and active only under direct sunlight in pre-metabolism genesis era.

- Natural selection is ubiquitous for ALL mass formats. It derives from the expansion of the universe.

- Epigenetics: Where Life Meets the Genomehttp://www.bionews.org.uk/page_66997.asp?dinfo=rWfnKzZO4tkhJf38jsJ5EeJo

Epigenetics = a) the study of heritable changes in gene function that do not involve changes in DNA sequenceb) the science of enduring changes in the pattern of gene activity, during embryo development and beyond, that do not involve alteration of the DNA sequence.

The "heritable or enduring changes" are epiDNAtics, not epigenetics. Alternative splicing is not epigenetics, even if/when not involving alteration of the DNA sequence. Earth life is an RNA world.

It's the RNAs that evolve proteins. AND IT'S THE RNAs THAT HAVE EVOLVED AND PRODUCE AND EMPLOY THE DNA templates to carry out life processes, for enhancing Earth's biosphere, for enhancing and constraining as long as possible some energy, some of the total energy of the universe, all of which is destined to fuel the ongoing cosmic expansion.

Glaciers on the surface of Pluto could explain the mysterious frozen world's youthful skin. Also: most Earth-like planet ever found orbiting a Sun-like star, and more support for the Standard Model of particle physics.